Enhanced capillary zone electrophoresis and apparatus for performance thereof

Abstract

Capillary zone electrophoresis is enhanced by the application of an electric field across the interior of the capillary tube. This external electric field is applied through a conductive member at the exterior of the capillary tube. The external field vectorially couples with the internal field, controlling the polarity and the magnitude of the surface (zeta) potential on the interior surface of the capillary. The control of the surface (zeta) potential reduces adsorption of macromolecular onto the interior surface of the capillary tube, by inducing electrostatic repulsions between the macromolecules, and the capillary surface. Additionally, the control of the surface (zeta) potential can retard, and even reverse, electroosmotic flow, depending upon the magnitude of those fields.

What is claimed is: 
     
       1. A method of separating elements of a mixture of substances in a solution or suspension by conducting capillary electrophoresis of said solution or suspension, said electrophoresis inducing an electroosmotic flow in said solution or suspension, said method comprising: 1) applying an internal electric field internally along the length of a capillary tube having an interior filled with said solution or suspension bound by a capillary wall,   2) applying an external electric field across the interior of said capillary tube through a conductive member exterior to the interior of said capillary tube,   3) wherein the electric potential difference between the internal and external fields produces an electric field perpendicularly across the capillary wall, along the length of said tube, thereby altering the electroosmotic flow rate, and   4) permitting said solution to undergo electrophoresis under the influence of said electric fields, whereby separation of said elements is optimized.   
     
     
       2. The process of claim 1, wherein said element comprises biomolecules. 
     
     
       3. The process of claim 1, wherein said element comprises protein molecules. 
     
     
       4. The process of claim 1, wherein said process further comprises forming micelles in said suspension which micelles are resolved by micellar capillary electrophoresis. 
     
     
       5. The process of claim 1, wherein said electric potential difference is non-uniform along the length of said tube. 
     
     
       6. The method of claim 1, wherein the absolute value in the electric potential difference is up to 6 Kv. 
     
     
       7. The process of claim 3, wherein said capillary tube comprises silica, and said interior surface is free of any coating on said silica. 
     
     
       8. A method for improving resolution of components of a liquid composition comprising a solution or suspension through capillary electrophoresis, comprising: 1) filling a capillary tube with said liquid composition,   2) applying an internal electric field along the length of said capillary tube to cause components in said liquid composition to undergo electrophoretic migration in the direction of said internal field, thereby inducing electroosmotic flow in said tube, and   3) altering said electrophoretic migration by applying an electric field across the interior of said capillary tube from a source exterior to said tube, thereby causing the electroosmotic flow induced to change, improving resolution of the components of said suspension.   
     
     
       9. The method of claim 8, wherein said electroosmotic flow rate is increased. 
     
     
       10. The method of claim 8, wherein said electroosmotic flow rate is decreased. 
     
     
       11. The method of claim 8, wherein the strength of said electric field applied across the interior of said capillary is altered during said resolution process. 
     
     
       12. The method of claim 8, wherein said field applied across the capillary tube in step c is of such dimension as to halt electroosmotic flow in said tube. 
     
     
       13. The method of claim 8, wherein said field applied across the capillary tube in step c is of dimension sufficient to reverse the direction of said induced electroosmotic flow.